In the past, I've had Akvorado configured with

• clickhouse.kafka.consumers: 12
• kafka.topic-configuration.num-partitions: 12

for testing purposes, but changed both back to 5 some time ago.

However, running kafka-consumer-groups.sh --bootstrap-server localhost:9092 --describe --group clickhouse still shows 12 "active" partitions (ones with values at CURRENT-OFFSET, LOG-END-OFFSET and LAG) for one topic flows-243Q[…] and, surprising to me, six ones for another topic flows-LAAB[…] where no data seems to go through (no values for CURRENT-OFFSET, LOG-END-OFFSET and LAG) but still for each partition there is a clickhouse consumer and client connected. Any idea what's up with these?

Regarding the number of partitions, there's also this log entry:

Nov 18 10:47:57 akvorado akvorado[872591]: {"level":"warn","brokers":"127.0.0.1:9092","topic":"flows-243QR3DRGFU3LAWDAIZA7TXBYM","time":"2024-11-18T10:47:57+01:00","caller":"akvorado/orchestrator/kafka/root.go:93","module":"akvorado/orchestrator/kafka","message":"cannot decrease the number of partitions (from 12 to 5)"}

OK, a quick search reveals: reducing the number of partitions isn't supported by Kafka.

Is there some way to reduce the number of partitions (and more important the number of consumers) anyway? I wouldn't care about data loss as I have huge performance problems currently (12 clickhouse consumers on 12 CPU cores don't work out very well).

I've already tried deleting all of /var/lib/kafka but it didn't work.

That's in advance.